Pyridoxamine (pyridoxine) 5'-phosphate oxidase will be examined for the function of all possible catalytically reactive amino acid residues and total amino acid composition. Affinity techniques will be developed for purification of a second form. The biosynthesis in vitro of the covalent 8 alpha-histidylFAD of succinate dehydrogenase will be investigated for the liver mitochondrial system. Further examination of the relatve orientations and interactions of amino acid residues and 8 alpha-cysteinyl flavin within the active site of mitochondrial monoamine oxidase will be done. Synthesis of the active-site flavinyl peptide from a Chromatium cytochrome c reductase with a presumed thiohemiacetal linkage will be initiated to determine the cause for attachment stability. Flavin coenzyme analogs that are functional with certain flavoproteins but have different spectral and redox properties will be used as active-site probes. BIBLIOGRAPHIC REFERENCES: Shih, J.C.H., Rozo, M.L., Wright, L.D., and McCormick, D.B. (1975). Characterization of the growth of Pseudomonas putida LP on lipoate and its analogues: Transport, oxidation, sulphur source, and enzyme induction. J. Gen. Microbiol. 86: 217-227. Johnson, P.G., Bell, A.P., and McCormick, D.B. (1975). Flavin-sensitized photooxidation of histidine. Photochem. Photobiol. 21: 205-208.